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以苯乙烯悬浮聚合为体系,考察羟基磷酸钙(HAP)或HAP与聚乙烯醇(PVA)复合为分散剂体系时,各种因素如分散剂浓度、油水比、搅拌速度等与瞬时液滴大小及分布之间的关系,并分析讨论瞬时液滴分散、合并的过程特征.结果表明,悬浮苯乙烯液滴聚合宏观成粒的特征与分散剂的分散机理无关,仅体现液滴分散、合并的过程特点.当采用分批加分散剂时,实验观察到瞬时液滴大小分布呈由单峰过渡到双峰,再发展成单峰分布的特征,从而找出了以分批加分散剂方式制备窄分布聚合物颗粒的理论依据. 相似文献
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在分析研究分散相黏度对液滴变形和破碎影响的基础上,提出了一个改进的液滴破碎频率模型并拓展了液滴破碎判据标准.同时通过Monte Carlo模拟的随机方法,得到了湍流搅拌槽中液-液分散体系的液滴直径分布和Sauter平均直径d32.通过与文献中关于d32的实验结果比较发现,该模型预测的Sauter平均直径更接近实验值,对于黏性分散相改进的液滴破碎频率模型要优于Coulaloglou和Tavlarides提出的模型.计算结果表明对于黏性分散相液滴,其黏度限制了液滴变形,使得液滴破碎频率被大大减少, 液滴直径明显增加,液滴直径分布向右偏移. 相似文献
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旋流塔板上液滴的运动模型 总被引:4,自引:0,他引:4
以液滴离开塔板的初始位置为边缘分布、液滴粒径为条件分布,用概率统计的方法来描述旋流塔板上液滴群运动的边界条件,进而提出其三维模型。该模型不含可调参数,采用四阶Runge-Kutta法计算,结果得到实验的支持。 相似文献
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基于FLUENT软件的管式搅拌反应器流场的数值模拟 总被引:2,自引:0,他引:2
运用商业计算流体力学(CFD)软件FLUENT对一种新型管式搅拌反应器进行流场模拟,用GAMBIT建立流场实体模型,采用标准k-ε湍流模型以及多重参考系法(MRF)处理搅拌桨区.结果表明,计算所选模型能较准确地预测搅拌反应器的速度场、压力场及湍流动能分布,考察流量为1 m3/h时不同搅拌转速对反应器内部混合的影响,此时对应的最佳搅拌转速为50 rpm左右.模拟结果将为实验研究提供适当的操作参数,对搅拌反应器的优化和放大具有一定参考价值. 相似文献
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Theoretical studies have been made through a unified nondimenslonal numerical model to evaluate the evaporation, drop size distribution and entropy generation characteristics of an atomized spray of liquid containing dissolved solids in a uniform stream of gas at high temperature. The influence of pertinent input parameters, namely, the initial concentration, initial Reynolds number of the spray and the ratio of ambient to initial drop temperature on the evaporation, drop size distribution and entropy generation histories of the spray with its down stream distance have been established. 相似文献
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Theoretical studies have been made through a unified nondimenslonal numerical model to evaluate the evaporation, drop size distribution and entropy generation characteristics of an atomized spray of liquid containing dissolved solids in a uniform stream of gas at high temperature. The influence of pertinent input parameters, namely, the initial concentration, initial Reynolds number of the spray and the ratio of ambient to initial drop temperature on the evaporation, drop size distribution and entropy generation histories of the spray with its down stream distance have been established. 相似文献
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压降比和分流比是油水分离旋流器的重要操作参数,我们通过全因素试验研究了这两个参数之间的关系,以及结构参数对该关系的影响。我们发现压降比与分流比的关系仅与旋流器的结构参数有关,与操作参数无关;压降比与分流比的关系是非线性的,其非线性程度随溢流口直径的减小而增强,当分流比较小时近似处理为线性会造成较大误差;尾管尺寸对压降比与分流比关系曲线的起点和变化率影响较大;进口尺寸对压降比与分流比关系曲线的起点影响很大,对其变化率影响较小;锥度对压降比与分流比关系曲线的起点影响较小,对其变化率有一定影响,特别是锥度较大时较明量。 相似文献
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This paper focuses on the mathematical modeling of the two-stage extraction using the single drop technique. Two stages of extraction are being considered: the drop formation step, where dimensions of the drop are highly dependent on time, and the drop travel step, during which the drops size and dimensions are assumed constant. Models for both extraction steps are derived and the combined model is proposed. Two-stage and one-stage models of extraction are compared. Errors occuring when considering only the travel stage of the single drop extraction have been calculated and their dependencies on various extraction parameters have been determined. The analysis of the combined two-stage model has proven that the travel-stage-only model generates significant errors during the determination of reaction rate constants when the drop formation time is significant in relation to the whole extraction time. Thus, the two-stage model should be used to reduce originating errors. 相似文献
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An improved stagewise model has been developed to represent more accurately the physical processes occurring in a liquid—liquid extraction column. The influence of drop size distribution is more realistically represented in this model. The model equations have been solved numerically with a range of parameter values in order to predict the extent of the influence of drop size distribution on extraction rates. Drop size distributions, measured in a turbine-agitated column section and inserted into the model equations, gave predictions of a considerable influence of size distribution on extraction column performance. 相似文献
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本文研究了气升式内环流反应器中油滴的分散特性。以对数正态分布密度函数为油滴尺寸的分散模型,导出了油滴的Sauter平均直径解析式。对模型作了实验验证,关联了模型参数。提出了油滴的尺寸分布密度函数和Sauter平均直径的半经验式。结果表明计算值与实验值吻合良好。 相似文献
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A theoretical and experimental study of direct contact heat transfer in a kerosene-water spray column has been carried out. A mathematical model for the process with a drop size distribution is proposed, and the associated computer program for the numerical solution developed. Correlations for the overall area heat transfer and axial dispersion coefficients for the column were obtained. Applying the mathematical model with experimentally obtained parameters, temperature profiles of both phases could be predicted. Comparisons with previous work in the literature support the present study. From the results, operation with uniform drop size in a short column is recommended. 相似文献
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Pressure drop and concentration distribution studies for the flow of multi-sized solid-liquid flow through slurry pipelines has been carried out over a wide range of efflux concentrations and mixtures of solids having different particle size distributions. The particle size effect on pressure drop has been analyzed through the measured solid distribution pattern in the pipeline. An integral flow model has been used for prediction of the pressure drop and solids distribution under various conditions. The model has been used to predict the optimum particle size distribution that gives the minimum specific energy consumption. 相似文献
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Ville Alopaeus Jukka Koskinen Kari I. Keskinen 《Chemical Engineering Communications》2003,190(11):1468-1484
A simulation model has been developed to model drop populations in a mixed tank. A multiblock mixed tank model has been used with the drop population balance equations developed in the literature. The drop breakage and coalescence functions used in the population balance model take into account the local turbulent energy dissipation values. The drop breakage and coalescence function parameters are fitted against drop size measurements from dense liquid-liquid dispersions, which were assumed fully turbulent. Since the local turbulence and flow values of a mixed tank are used in the present model, the fundamental breakage and coalescence phenomena can be taken into closer examination. Furthermore, the present model is capable of predicting inhomogeneities occurring in a mixed tank. It is also considered as an improved tool for process scale-up, compared to the simple vessel-averaged population balance approach, or use of correlations of dimensionless numbers only. The present model can use two sources of data for fitting parameters in the drop rate functions. One is the transient data of the measured drop size distribution as the impeller speed is changed. The other is the time-averaged data measured at different locations of the mixed tank. Different flow regions can be chosen from direct measurements or from the CFD simulations in a straightforward manner. CFD flow simulation results can be used when no experimentally obtained flow conditions are available. This is especially useful for nonstandard vessels, such as reactors containing cooling coils. 相似文献
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Effect of scale on the drop size distribution in a pump-mix mixer has been studied. A network of zones model was developed to predict the drop size distribution at different locations in the mixer. Computational fluid dynamics model was used to obtain the flow patterns in the mixer and to identify zones based on the flow patterns. Population balance equation was solved for all the zones of the mixer. The model was validated with the experimental data over a wide range of parameters as well experimental data from the published literature. The model was further extended for scale-up studies. Two different scale-up criteria were studied. It was observed that equal power consumption per unit mass and geometrical similarity is a better scale-up criterion as compared with equal tip speed criterion for pump-mix mixers. 相似文献